The subject matter herein relates generally to relay assemblies, and more particularly, to methods and apparatus for reducing bounce during mating of a movable relay contact with a stationary relay contact.
Bouncing of relay and switch button-style contacts is a well known phenomenon, and is typically caused by a combination of factors. The factors include the initial impact and rebound of the contacts, flexing of a beam carrying a movable one of the contacts, the impact between an armature plate carrying the beam and a core of the relay, and/or the propagation of the impacts along the contact beam. Contact bouncing can have the effects of creating electrical noise within the system using the relay or switch and/or damaging the contacts themselves. Bouncing breaks and re-makes the electrical connection at and below the millisecond time-frame. That action generates various stages of arcing causing very broadband noise to be imposed on, and radiated to, connected and surrounding electrical systems. This noise can cause many types of malfunctions and interference. Systems using known relays provide filtering and shielding to diminish the interference or malfunction at an increase in the cost of the overall systems.
Damage to the contacts is generally caused by electrical arcing between the contacts when the contacts are separated from one another, such as during the bouncing of the contacts. Damage to the contacts limits the life and sets the maximum switching energy limits of the device. Many special materials have been developed to withstand the damaging effects long enough to achieve an acceptable service life. Increased contact mass, high velocity action and high forces are needed to enable high switching energy ratings. These limit the size, weight and cost reductions that can be achieved.
Conventional relays address the problems associated with contact bouncing by attempting to reduce the amount of bouncing or by using materials that sustain the wear caused by the arcing. These known relays attempt to reduce the amount of bouncing by using a dampening material on at least one of the contact structures to reduce the rebound after initial impact, by providing a counterweight that impacts the beam or contact at the time of rebound, or by counteracting the rebound with a device, such as a spring to hold the contact against rebound. These solutions are complicated and costly, and do not eliminate the bounce between the contacts. Similarly, the known relays that use materials that sustain wear caused by arcing are costly and the material adds bulk and weight to the contacts. As such, a relay assembly is needed that reduces the bouncing phenomenon in a cost effective and reliable manner.